(1) Field of the Invention
The present invention relates to a motor of a clothes washing machine.
(2) Description of the Related Art
Generally, a clothes washing machine includes a main body defining an outer configuration thereof, a water tub installed within the body, and a spin basket and blade mounted within the water tub. A power system for driving the spin basket and blade is mounted under the water reserving basket.
The power system typically comprises a motor, a power transmission system, and a belt for connecting the motor to the power transmission system. This will be described hereinbelow with reference to FIG. 6.
As shown in the drawing, a conventional power system comprises a power transmission system 100 having a drive motor (not shown). The power transmission system 100 comprises a hollow dehydrating (spin-dry) shaft 101 and a laundering shaft 102 inserted into the hollow dehydrating shaft 101. The laundering shaft 102 is divided into upper and lower halves, with a planetary gear unit 103 being disposed therebetween. The planetary gear unit 103 changes a rotating speed of the power transmission system 100.
A brake band 104 and a brake lever 105 are disposed beside the dehydrating shaft 101 to brake the rotation of the dehydrating shaft 101, for suppressing an idle rotation of the spin basket 110. A one-way bearing 106, permitting the dehydrating shaft 101 to rotate in only one direction, is mounted on an outer circumference of the dehydrating shaft 101. In addition, a clutch spring 107 and a clutch lever 108 for transmitting/interrupting power from the motor to the dehydrating shaft 101 or the laundering shaft 102 are mounted under the one-way bearing 106. A pulley 109 on which a belt (not shown) is engaged is mounted on a lower end of the laundering shaft 102.
In this conventional power transmission system 100, torque of the motor is selectively transmitted to either a rotating blade 111 or to both the blade 111 and the spin basket 110 through the clutch spring 107, thereby performing the washing and dehydrating operations respectively. To achieve this, it is necessary that the clutch spring 107 has a high degree of tensile strength to enable the transmission or interruption of torque from the motor to either the dehydrating shaft 101 or the laundering shaft 102, both of which are rotated at a high speed. However, the manufacturing process for such a spring having high tensile strength is complicated, and, as a result, manufacturing costs are increased.
In addition, the brake band 104 for preventing the spin basket 110 from idling rotationally during the washing operation is, when it brakes the spin basket 110 in one direction, subjected to high resistance against force generated when the spin basket 110 is acted on by a water current within the water tub. The above described one-way bearing 106 must be used as a result, making the structure complicated and increasing manufacturing costs. Finally, an unpleasant noise is generated during the braking operation of the brake band.
As described above, the conventional power system of a washing machine is complicated with regard to the arrangement of parts for performing the washing, dehydrating and braking operations, making it difficult to manufacture the same and increasing manufacturing costs. In addition, because of the large number of parts needed for this complicated arrangement, much space is required which, in turn, acts to increase the overall size of the washer.
To solve the above described problems, in recent years, a direct-coupled washing machine in which the power transmission system is directly connected to the motor has been developed. A brushless direct current motor is used for the direct-coupled washing machine. The brushless direct current motor is reversible and capable of increasing and decreasing the rotating speeds. The brushless direct current motor is designed to operate by electromagnetic induction between a stator and magnets mounted on a rotor.
However, when the motor is operated, variable magnetic force acts on a core of the stator, generating an eddy current and causing loss of hysteresis by the change in magnetizing force. The eddy current and hysteresis loss results in a heating of the stator, and, if the stator becomes over-heated, the driving efficiency of the motor deteriorates, reducing the life span of the motor.